Support structure for linear-compressor moving component, linear compressor, and cryogenic refrigerator

ABSTRACT

A linear-compressor moving component support structure includes: a plurality of leaf spring parts each elastically supporting the moving component in the compressor container such as to allow its axially reciprocating movement; a plurality of first auxiliary spring parts, each of which has first axial rigidity and is located adjacent to one of opposite sides of a corresponding leaf spring part; and a plurality of second auxiliary spring parts, each of which has second axial rigidity and is located adjacent to the other of the opposite sides of a corresponding leaf spring part. The second axial rigidity is different from the first axial rigidity such as to correct deviation, arising due to pressure differences between the high- and low-pressure chambers exerted on the moving component, of actual range of axial movement of the moving component from a predetermined range of axial movement of the moving component.

RELATED APPLICATION

Priority is claimed to Japanese Patent Application No. 2014-206157, filed on Oct. 7, 2014, the entire content of which is incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Technical Field

The present invention relates to a movable body support structure, a linear compressor, and a cryogenic refrigerator.

2. Description of Related Art

Linear compressors that compress a working gas by axial movement of a moving component such as a piston are known. Movement of the moving component reduces the volume of the compressor's compression chamber, compressing the working gas inside. The moving component is elastically supported by means of a spring such as a leaf spring or a coil spring. Normally, movement of the moving component is axial oscillatory motion.

In linear compressors, axially reciprocating movement of the moving component produces a cyclic change in volume of the compression chamber. The range of the reciprocating movement is defined by design so as to attain desired compressor performance (e.g., efficiency). However, depending on the design or operating conditions of the linear compressor, the moving component can become displaced due to differences in compression-chamber pressure exerted upon the moving component as it reciprocates. As a consequence, the moving component may reciprocate through an axial range slightly different from the predefined range of its axial movement. This can change the volume of the compression chamber, and thus have an impact the efficiency of the linear compressor.

The center of the reciprocating movement of the moving component is defined by design to be in a specified position (e.g., in the neutral position of the leaf spring). If the range of axial movement of the moving component deviates from the predefined range as described above, the center of movement also will be displaced from the predefined position. The more distanced the center of movement from the neutral position of the spring, the heavier the load exerted on the spring, resulting in reduced life of the spring.

SUMMARY

Embodiments of the present invention address a need to provide a movable body support structure capable of causing a movable body to make a reciprocal movement in a predefined range of axial movement in a linear compressor.

According to an embodiment of the present invention, there is provided a linear-compressor moving component support structure, comprising: a moving component partitioning a compressor container of the linear compressor into a high-pressure chamber and a low-pressure chamber for a working gas, the moving component being configured to reciprocate periodically along axially opposite directions in a predetermined range of axial movement, in one of the opposite directions of which the moving component compresses the working gas in the high-pressure chamber; a plurality of axially arranged leaf spring parts, each leaf spring part elastically supporting the moving component in the compressor container such as to allow the axially reciprocating movement of the moving component; a plurality of axially arranged first auxiliary spring parts each having a first axial rigidity, each first auxiliary spring part being located adjacent to one of opposite sides of a corresponding one of the plurality of leaf spring parts; and a plurality of axially arranged second auxiliary spring parts each having a second axial rigidity, each second auxiliary spring part being located adjacent to the other of the opposite sides of a corresponding leaf spring part. The second axial rigidity is different from the first axial rigidity such as to correct deviation, arising due to pressure differences between the high- and low-pressure chambers exerted on the moving component, of actual range of axial movement of the moving component from the predetermined range of axial movement of the moving component.

According to an embodiment of the present invention, there is provided a linear-compressor moving component support structure, comprising: a moving component partitioning a compressor container of the linear compressor into a high-pressure chamber and a low-pressure chamber for a working gas, the moving component being configured to reciprocate periodically along axially opposite directions, in one of the opposite directions of which the moving component compresses the working gas in the high-pressure chamber; a fixed body slidably supporting the moving component axially, and between itself and the moving component forming the high pressure chamber; an intake valve disposed in the moving component so as to supply the working gas from the low pressure chamber to the high pressure chamber; an outlet valve disposed in the fixed body so as to discharge the working gas from the high pressure chamber; a plurality of axially arranged leaf spring parts, each leaf spring part elastically supporting the moving component in the compressor container such as to allow the axially reciprocating movement of the moving component; a plurality of axially arranged first auxiliary spring parts each having a first axial rigidity, each first auxiliary spring part being located adjacent to one of opposite sides of a corresponding one of the plurality of leaf spring parts; and a plurality of axially arranged second auxiliary spring parts each having a second axial rigidity greater than the first axial rigidity, each second auxiliary spring part being located adjacent to the other of the opposite sides of a corresponding leaf spring part.

Optional combinations of the aforementioned constituting elements, and implementations of the invention in the form of methods, apparatuses, and systems may also be practiced as additional modes of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments will now be described, by way of example only, with reference to the accompanying drawings which are meant to be exemplary, not limiting, and wherein like elements are numbered alike in several Figures, in which:

FIG. 1 is a cross sectional view schematically showing a linear compressor according to an embodiment of the present invention;

FIG. 2 shows a cross section along a dashed line A-A in FIG. 1;

FIG. 3 is a schematic diagram showing a part of the leaf spring unit according to an embodiment of the present invention; and

FIG. 4 is a schematic diagram showing a cryogenic refrigerator according to an embodiment of the present invention.

DETAILED DESCRIPTION

The invention will now be described by reference to the preferred embodiments. This does not intend to limit the scope of the present invention, but to exemplify the invention.

A detailed description of an embodiment to implement the present invention will be given with reference to the drawings. Like numerals are used in the description to denote like elements and the description is omitted as appropriate. The structure described below is by way of example only and does not limit the scope of the present invention.

FIG. 1 is a cross sectional view schematically showing a linear compressor 10 according to an embodiment of the present invention. FIG. 2 shows a cross section along a dashed line A-A in FIG. 1. The linear compressor 10 includes a compressor housing 12, a compressor container 14, a piston 16, a cylinder 18, a linear actuator 20, and a leaf spring unit 22. The linear compressor 10 is provided with a single piston 16 and a single cylinder 18 that accepts the piston 16. The linear compressor 10 is configured as an unlubricated linear compressor (oilless linear compressor) in which oil is not used for lubrication of movable elements.

The compressor housing 12 accommodates the compressor container 14. Between the compressor housing 12 and the compressor container 14 is provided a dynamic absorber 24 for preventing or reducing transmission of the vibration of the compressor container 14 outside. The compressor housing 12 may be a cover member that covers the dynamic absorber 24.

The compressor container 14 is a pressure vessel configured to contain the working gas of the linear compressor 10 hermetically. For example, the working gas is a helium gas. The compressor container 14 accommodates the piston 16, the cylinder 18, the leaf spring unit 22, and the linear actuator 20.

Inside the compressor container 14 are included a high pressure chamber 26 and a low pressure chamber 28 for the working gas. An outlet pipe 30 is connected to the high pressure chamber 26 and an inlet pipe 32 is connected to the low pressure chamber 28. The outlet pipe 30 extends through the compressor housing 12 and the compressor container 14 and connects the high pressure chamber 26 to a space outside the linear compressor 10. The inlet pipe 32 extends through the compressor housing 12 and the compressor container 14 and connects the low pressure chamber 28 to a space outside the linear compressor 10. Therefore, a low pressure working gas 34 is collected from outside the linear compressor 10 into the low pressure chamber 28 via the inlet pipe 32. A high pressure working gas 36 is supplied from the high pressure chamber 26 to a space outside the linear compressor 10 via the outlet pipe 30.

In addition to or in place of the compressor container 14, the compressor housing 12 may be configured as a pressure vessel to contain the working gas of the linear compressor 10 hermetically.

The piston 16 is a movable body that provides a partition between the high pressure chamber 26 and the low pressure chamber 28 inside the compressor container 14. The high pressure chamber 26 includes a pressurizing chamber 38 and an outlet chamber 40. The pressurizing chamber 38 is formed between the piston 16 and the cylinder 18. The outlet chamber 40 is formed inside the cylinder 18. The outlet pipe 30 is connected to the outlet chamber 40.

The piston 16 is provided with an intake valve 42 for supplying the low pressure working gas 34 from the low pressure chamber 28 to the high pressure chamber 26. The intake valve 42 is opened or closed in accordance with a pressure difference between the high pressure chamber 26 and the low pressure chamber 28. If the pressure difference is less than a predetermined threshold value, the intake valve 42 is opened. If the pressure difference exceeds the threshold value, the intake valve 42 is closed. The cylinder 18 is provided with an outlet valve 44 for discharging the high pressure working gas 36 from the outlet chamber 40. The outlet valve 44 is opened or closed in accordance with a pressure difference between the high pressure chamber 26 and the outlet pipe 30. If the pressure difference exceeds a predetermined threshold value, the outlet valve 44 is opened. If the pressure difference is less than the threshold value, the outlet valve 44 is closed. Thus, the linear compressor 10 is configured as a valved linear compressor.

The piston 16 is a hollow cylindrical member extending in the axial direction (vertical direction in FIG. 1). The piston 16 includes a piston end 46 facing the pressurizing chamber 38 and a piston main body 48 extending from the piston end 46 away from the pressurizing chamber 38 in the axial direction. The piston end 46 is formed with a first piston recess 50 and the piston main body 48 is formed with a second piston recess 52. The first piston recess 50 is a hollow portion of the piston end 46 and forms a part of the pressurizing chamber 38. The second piston recess 52 is a hollow portion of the piston main body 48 and forms a part of the low pressure chamber 28.

Between the piston end 46 and the piston main body 48 is provided a piston partition 54. The piston partition 54 is a wall partitioning the first piston recess 50 and the second piston recess 52. A piston communication hole 56 is formed at the center of the piston partition 54. The piston communication hole 56 allows the first piston recess 50 and the second piston recess 52 to communicate with each other. The intake valve 42 is accommodated in the first piston recess 50. The intake valve 42 is configured so as to open or close the piston communication hole 56 in accordance with a pressure difference between the first piston recess 50 and the second piston recess 52.

The piston 16 is supported by the leaf spring unit in the compressor container 14 such that it can make a reciprocal movement in the axial direction (e.g., make an oscillatory motion). The radially inward portion of the leaf spring unit 22 is mounted to the base of the piston main body 48 so as to surround the piston 16 in the circumferentially direction. The radially outward portion of the leaf spring unit 22 is mounted to the compressor container 14.

The piston 16 also includes a piston driver 49 driven by the linear actuator 20. The piston driver 49 is mounted to the piston main body 48.

The cylinder 18 is a hollow cylindrical member extending in the axial direction so as to accept the piston 16. The cylinder 18 is supported by and fixed to the compressor container 14. The cylinder 18 includes a cylinder fixed end 58 fixed to the compressor container 14 and a cylinder main body 60 extending from the cylinder fixed end 58 toward the piston 16 in the axial direction. The outlet chamber 40 is formed in the cylinder fixed end 58. The cylinder main body 60 includes a cylinder interior surface 62 that slidably supports the piston 16 in the axial direction. Between the cylinder fixed end 58 and the cylinder main body 60 is provided a cylinder partition 64. A cylinder communication hole 66 is formed at the center of the cylinder partition 64. The cylinder communication hole 66 allows the outlet chamber 40 and the pressurizing chamber 38 to communicate with each other.

The linear actuator 20 is configured to drive the axial reciprocal movement of the piston 16. The piston 16 is driven by the linear actuator 20 so as to advance and recede in the axial direction periodically. The piston 16 advances in the upward direction in FIG. 1 and recedes in the downward direction in FIG. 1. For example, the linear actuator 20 is a linear oscillatory actuator for causing the piston 16 to make an oscillatory motion in the axial direction.

The leaf spring unit 22 is a bearing that permits axial reciprocal movement of the piston 16 and restricts radial or circumferential movement of the piston 16. The leaf spring unit 22 includes a plurality of leaf spring parts 23. The leaf spring unit 22 includes a plurality of first auxiliary spring parts 68 and a plurality of second auxiliary spring parts 70 in addition to the plurality of leaf spring parts 23. Details will be discussed with reference to FIGS. 2 and 3.

The plurality of leaf spring parts 23 are arranged in series in the axial direction and include, for example, at least ten leaf spring parts 23. The plurality of leaf spring parts 23 elastically supports the piston 16 in the compressor container 14 so that each leaf spring part 23 allows axial reciprocal movement of the piston 16. Each leaf spring part 23 extends along a plane perpendicular to the axial direction. For example, each of the plurality of leaf spring parts 23 is a single leaf spring. However, the leaf spring parts 23 may be configured otherwise. Each leaf spring part 23 may include a plurality of leaf springs stacked in the axial direction.

The plurality of leaf spring parts 23 are located adjacent to each other at certain axial spacing. The leaf spring parts 23 are arranged at axial spacing such that the leaf spring parts 23 do not contact each other. For example, the spacing between two axially adjacent leaf spring parts 23 is defined so that the two leaf spring parts 23 do not contact each other due to the elastic deformation caused by the reciprocal movement of the piston 16. A spacer or a holding member may be provided between the two leaf spring parts 23 in order to maintain an appropriate spacing.

As shown in FIG. 2, the leaf spring part 23 includes a leaf spring inner circumferential portion 72, a leaf spring outer circumferential portion 74 surrounding the leaf spring inner circumferential portion 72, and a plurality of elastic arms 76 (three arms in the case of FIG. 2) connecting the leaf spring inner circumferential portion 72 and the leaf spring outer circumferential portion 74. The leaf spring inner circumferential portion 72 is fixed to the piston 16 (e.g., the piston main body 48). The leaf spring outer circumferential portion 74 is fixed to the compressor container 14. Elastic deformation of the elastic arm 76 permits relative axial displacement between the leaf spring inner circumferential portion 72 and the leaf spring outer circumferential portion 74, i.e., axial displacement of the piston 16 relative to the compressor container 14.

The leaf spring part 23 configured as described above is called a flexure spring and is flexible in the direction of reciprocal movement of the piston 16 and is rigid in a direction perpendicular to the direction of reciprocal movement. Such a leaf spring is disclosed in, for example, JP2008-215440 and JP2013-195043. The entirety of these documents is incorporated herein by reference.

In this way, an axial oscillatory motion system having the piston 16 as a mass element and the leaf spring unit 22 as an elastic element is built. The oscillatory motion system is designed so as to give a desired resonance frequency by appropriately setting the axial rigidity of each leaf spring part 23 of the leaf spring unit 22. The oscillatory motion system is driven by the linear actuator 20.

The range of axial movement of the piston 16 is designed so as to give a desired cycle of volume change to the high pressure chamber 26 (e.g., the pressurizing chamber 38). The range of axial movement of the piston 16 may be defined such that the piston 16 (e.g., the piston end 46) contacts the portion of the cylinder 18 facing the piston 16 (e.g., the cylinder partition 64) as the piston 16 advances and reaches the top dead point, and the end surface of the piston 16 is spaced apart by a predetermined distance from the portion of the cylinder 18 facing the piston 16 as the piston 16 recedes and reaches the bottom dead point. Alternatively, the range of axial movement may be defined such that the end surface of the piston 16 does not contact the portion of the cylinder 18 facing the piston 16 and is spaced apart therefrom by a certain distance.

The range of axial movement of the piston 16 may alternatively be defined such that the central position of the periodic axial elastic deformation of the leaf spring parts 23 caused by the reciprocal movement of the piston 16 is aligned with the neutral position of the leaf spring parts 23.

A description will now be given of the basic operation of the linear compressor 10. As described above, the low pressure working gas 34 is collected from outside the linear compressor 10 into the low pressure chamber 28 via the inlet pipe 32. When the piston 16 is at the bottom dead point or moves in the neighborhood thereof, the intake valve 42 is opened and the outlet valve 44 is closed. The low pressure working gas 34 is supplied from the second piston recess 52 to the pressurizing chamber 38 via the piston communication hole 56. When the piston 16 advances from the bottom dead point toward the top dead point, the intake valve 42 is closed and the working gas in the pressurizing chamber 38 and the outlet chamber 40 is compressed to raise its pressure.

When the piston 16 is at the top dead point or moves in the neighborhood thereof, the outlet valve 44 is opened and the high pressure working gas 36 is supplied outside the linear compressor 10 from the outlet chamber 40 via the outlet pipe 30. When the piston 16 recedes from the top dead point toward the bottom dead point, the outlet valve 44 is closed and the working gas in the pressurizing chamber 38 and the outlet chamber 40 is expanded to lower its pressure. When the piston 16 returns to the bottom dead point or in the neighborhood thereof, the intake valve 42 is opened and the low pressure working gas 34 is supplied to the pressurizing chamber 38 again. In this way, the compression cycle in the linear compressor 10 is repeated.

Ideally, the piston 16 makes an oscillatory motion during the compression cycle in a range of axial movement as designed. The center of oscillatory motion is aligned with the neutral position of the leaf spring parts 23. We have found that the piston 16 in such a valved linear compressor is slightly pressed from the high pressure chamber 26 as it makes an oscillator motion, due to the pressure difference exerted on the piston 16 during the compression cycle. For this reason, the actual range of axial movement of the piston 16 is slightly deviated from the range of axial movement as designed toward the low pressure chamber 28. This increases the volume of the pressurizing chamber 38 throughout the compression cycle. In particular, the volume of the pressurizing chamber 38 occurring when the piston 16 is located at the top dead point is increased so that the efficiency of the linear compressor 10 can be reduced. The further away the center of oscillator motion is from the neutral position of the leaf spring parts 23, the heavier the load exerted on the leaf spring parts 23 at the top dead point or the bottom dead point. If a high load continues to be exerted, the life of the leaf spring parts 23 can be reduced. Methods to address these issues will be described below in detail.

A typical leaf spring support is configured such that the axial rigidity is symmetrical in respective directions of reciprocal movement. In contrast, the axial rigidity of the leaf spring unit 22 according to the embodiment is configured to be asymmetrical. In other words, the leaf spring unit 22 is designed such that the axial rigidity in one direction of reciprocal movement is different from that of the opposite direction. Therefore, the second auxiliary spring parts 70 of the leaf spring unit 22 have axial rigidity different from that of the first auxiliary spring parts 68. This corrects deviation of the actual range of axial movement of the piston 16 from the range of axial movement as designed created due to the pressure difference between the high pressure chamber 26 and the low pressure chamber 28 exerted on the piston 16.

More specifically, the leaf spring unit 22 is configured such that the axial rigidity in the direction of receding toward the low pressure chamber 28 is greater than the axial rigidity in the direction of advancing toward the high pressure chamber 26. Therefore, the axial rigidity of the second auxiliary spring parts 70 of the leaf spring unit 22 is greater than the axial rigidity of the first auxiliary spring parts 68. Therefore, the leaf spring unit 22 is less likely to be displaced from the neutral position toward the low pressure chamber 28. Deviation in axial position of the center of oscillatory motion of the piston 16 with respect to the neutral position of the leaf spring unit 22 is corrected such that the center of oscillatory motion of the piston 16 approaches or is aligned with the neutral position of the leaf spring unit 22. This suppresses deviation of the range of movement of the piston 16 toward the low pressure chamber 28.

FIG. 3 is a schematic diagram showing a part of the leaf spring unit 22 according to an embodiment of the present invention. As shown in FIGS. 2 and 3, each of the plurality of first auxiliary spring parts 68 is located adjacent to one side of the corresponding one of the plurality of leaf spring parts 23 (the side toward the pressurizing chamber 38; toward top in the figure). Each of the plurality of second auxiliary spring parts 70 is located adjacent to the opposite side of the corresponding one of the plurality of leaf spring parts 23 (the side away from the pressurizing chamber 38; toward bottom in the figure). FIG. 3 illustrates the outer portion of the first auxiliary spring parts 68 and the second auxiliary spring parts 70 fixed to the compressor container 14.

In the leaf spring unit 22, the first auxiliary spring part 68, the leaf spring part 23, and the second auxiliary spring part 70 are arranged in the stated order in the axial direction to constitute one unit, which is repeated in the axial direction. In other words, the first auxiliary spring part 68 and the second auxiliary spring part 70 are located adjacent to each other between two leaf spring parts 23 adjacent to each other in the axial direction.

At the neutral position, the first auxiliary spring part 68 may be provided in contact with the adjacent leaf spring part 23 or provided at a spacing from the adjacent leaf spring part 23. The same holds true of the second auxiliary spring part 70. A spacer or a holder member may be provided between the first auxiliary spring part 68 (or the second auxiliary spring part 70) and the adjacent leaf spring part 23.

Each first auxiliary spring part 68 is adjacent to one side of the corresponding leaf spring part 23 so as to follow the elastic deformation of the leaf spring part 23 toward that side, by coming into contact with the leaf spring part 23 as a result of the elastic deformation. Each second auxiliary spring part 70 is adjacent to the other side of the corresponding leaf spring part 23 so as to follow the elastic deformation of the leaf spring part 23 toward that side, by coming into contact with the leaf spring part 23 as a result of the elastic deformation. These auxiliary spring parts mitigate concentration of stress on the leaf spring part 23 elastically deformed, by following the elastic deformation of the leaf spring part 23.

The axial rigidity of each first auxiliary spring part 68 is defined to produce a desired benefit of mitigating concentration of stress on the adjacent leaf spring part 23. The axial rigidity of each second auxiliary spring part 70 is also defined to produce a desired benefit of mitigating concentration of stress on the adjacent leaf spring part 23. The difference is that the axial rigidity of the second auxiliary spring part 70 is different from the axial rigidity of the first auxiliary spring part 68, as described above.

As shown in FIG. 2, the first auxiliary spring part 68 includes an auxiliary spring inner portion 78 and an auxiliary spring outer portion 80. For convenience, FIG. 2 illustrates the first auxiliary spring part 68 (or the second auxiliary spring part 70) in dashed lines. The auxiliary spring inner portion 78 includes an auxiliary spring inner circumferential portion 82 and a plurality of (three, in the case of FIG. 2) inner cantilevered arms 84. The auxiliary spring inner circumferential portion 82 is fixed to the piston 16 (e.g., the piston main body 48). Each inner cantilevered arm 84 is located adjacent to one axial side of a joint between the leaf spring inner circumferential portion 72 and the elastic arm 76. The auxiliary spring outer portion 80 includes an auxiliary spring outer circumferential portion 86 and a plurality of (three, in the case of FIG. 2) outer cantilevered arms 88. The auxiliary spring outer circumferential portion 86 is fixed to the compressor container 14. Each outer cantilevered arm 88 is located adjacent to the other axial side of the joint between the leaf spring outer circumferential portion 74 and the elastic arm 76. The second auxiliary spring part 70 is configured similarly.

The end of the inner cantilevered arm 84 and the end of the outer cantilevered arm 88 are spaced apart from each other and are not joined. Thus, the auxiliary spring inner portion 78 and the auxiliary spring outer portion 80 are mutually isolated members. Therefore, unlike the leaf spring part 23, the first auxiliary spring part 68 and the second auxiliary spring part 70 do not support the piston 16 in the compressor container 14.

When the elastic arm 76 is elastically deformed in the axial direction in a compression cycle, the elastic arm 76 comes into contact with the inner cantilevered arm 84 and the outer cantilevered arm 88, causing the inner cantilevered arm 84 and the outer cantilevered arm 88 to be elastically deformed in the axial direction along with the elastic arm 76. This mitigates concentration of stress at the joint of the elastic arm 76.

As shown in FIG. 3, each of the plurality of first auxiliary spring parts 68 may include one or more one first auxiliary springs 69 arranged one over the other in the axial direction or arranged in a laminated manner in the axial direction. Each of the second auxiliary spring parts 70 may include one or more second auxiliary springs 71 arranged one over the other in the axial direction or arranged in a laminated manner in the axial direction.

The first auxiliary spring 69 has the same dimension as the second auxiliary spring 71 and is made of the same material as the second auxiliary spring 71. Therefore, the axial rigidity of the individual first auxiliary spring 69 is equal to the axial rigidity of the individual second auxiliary spring 71. However, the number of the first auxiliary springs 69 arranged one over the other in the axial direction according to the embodiment is different from the number of the second auxiliary springs 71 arranged one over the other in the axial direction. Therefore, the axial rigidity of the first auxiliary spring part 68 is different from the axial rigidity of the second auxiliary spring part 70. Since the first auxiliary springs 69 and the second auxiliary springs 71 are configured by using the same building blocks, there is no need to prepare special-purpose members for the first auxiliary spring part 68 and the second auxiliary spring part 70.

For example, a single first auxiliary spring 69 and two second auxiliary springs 71 are provided for each leaf spring part 23, as shown in FIG. 3. Therefore, the axial rigidity of the second auxiliary spring part 70 is greater than the axial rigidity of the first auxiliary spring part 68. Therefore, the amount of axial deformation of the leaf spring unit 22 in a compression cycle is smaller in the receding direction than in the advancing direction.

As described above, the axial rigidity of the second auxiliary spring part 70 is designed to be greater than the axial rigidity of the first auxiliary spring part 68 so as to correct deviation of the actual range of axial movement of the piston 16 from the range of axial movement as designed created due to the pressure difference between the high pressure chamber 26 and the low pressure chamber 28 exerted on the piston 16. Therefore, the piston 16 can make a reciprocal movement in the range of axial movement as designed or in the neighborhood thereof. In association with this, a desired volume change can be produced in the high pressure chamber 26 so that the linear compressor 10 can be operated to exhibit desired performance.

Further, since the axial rigidity of the second auxiliary spring part 70 is greater than the axial rigidity of the first auxiliary spring part 68, the central position of reciprocal movement is corrected such that the reciprocal movement of the piston 16 occurs at the neutral position of the leaf spring unit 22 or in the neighborhood thereof. Accordingly, an excessive load is prevented from being exerted on the leaf spring part 23.

Described above is an explanation based on an exemplary embodiment. The invention is not limited to the embodiment described above and it will be obvious to those skilled in the art that various design changes and variations are possible and that such modifications are also within the scope of the present invention.

In certain embodiments, special-purpose members may be prepared for the first auxiliary spring part and the second auxiliary spring part in order to make the axial rigidity of the first auxiliary spring part different from that of the second auxiliary spring part.

For example, the first auxiliary spring part may have a different dimension from that of the second auxiliary spring part. For example, the first auxiliary spring part may have a different axial thickness than the second auxiliary spring part. In this case, one first auxiliary spring and one second auxiliary spring may be provided for one leaf spring part and the first auxiliary spring and the second auxiliary spring may differ in thickness. The second auxiliary spring part may be thicker than the first auxiliary spring part in the axial direction so that the second auxiliary spring part has greater axial rigidity than the first auxiliary spring part.

Alternatively, the first auxiliary spring part may have a length different from that of the second auxiliary spring part in a plane perpendicular to the axial direction. For example, the inner (or outer) cantilevered arm of the first auxiliary spring part may have a length different from that of the inner (or outer) cantilevered arm of the second auxiliary spring part. The second auxiliary spring part may be longer than the first auxiliary spring part so that the second auxiliary spring part has greater axial rigidity than the first auxiliary spring part.

In certain embodiments, the first auxiliary spring part may be made of a material different from that of the second auxiliary spring part in order to make the axial rigidity of the first auxiliary spring part different from that of the second auxiliary spring part. The second auxiliary spring part may be made of a material more rigid than that of the first auxiliary spring part so that the second auxiliary spring part has greater axial rigidity than the first auxiliary spring part. For example, the first auxiliary spring part may be made of stainless steel and the second auxiliary spring part may be made of titanium magnesium alloy. In this case, the leaf spring part may also be made of stainless steel like the first auxiliary spring part.

In the illustrative embodiment described above, the second auxiliary spring part 70 is configured to have greater axial rigidity than the first auxiliary spring part 68 since the piston 16 is displaced toward the low pressure chamber 28 while the linear compressor 10 is being operated. However, the piston may be displaced toward the high pressure chamber during operation, depending on the design or the operating condition of the linear compressor. In certain embodiments, therefore, the axial rigidity of the second auxiliary spring part 70 may be smaller than the axial rigidity of the first auxiliary spring part 68.

In certain embodiments, the linear compressor may include a piston fixed to the compressor container and a cylinder configured to move axially with respect to the piston. In this case, the leaf spring unit may elastically support the cylinder in the compressor container so as to allow axial reciprocal movement of the cylinder.

In certain embodiments, an additional elastic member for elastically supporting the movable body of the linear compressor may be provided apart from the leaf spring unit. The elastic member may be provided between the movable body and the compressor container so as to energize the movable body toward the low pressure chamber (or the high pressure chamber) in the axial direction.

FIG. 4 is a schematic diagram showing a cryogenic refrigerator 100 according to an embodiment of the present invention. A cryogenic refrigerator 100 includes the linear compressor 10 and an expander 102. The outlet pipe 30 of the linear compressor 10 is connected to the expander 102 via a high pressure pipe 104. The inlet pipe 32 of the linear compressor 10 is connected to the expander 102 via a low pressure pipe 106. For example, the expander 102 is an expander of Gifford-McMahon type. The expander 102 may have a built-in valve part for selectively connecting the expansion chamber inside of the expander 102 to one of the outlet pipe 30 and the inlet pipe 32 of the linear compressor 10. The high pressure working gas 36 is supplied from the linear compressor 10 to the expander 102 via the high pressure pipe 104. The low pressure working gas 34 is collected from the expander 102 into the linear compressor 10 via the low pressure pipe 106.

A heat exchanger 108 for cooling (e.g., to the room temperature) the high pressure working gas 36 discharged from the linear compressor 10 may be provided outside the expander 102. The heat exchanger 108 may be provided in the middle of the high pressure pipe 104. In this way, the working gas having its temperature controlled appropriately may be supplied to the expander 102.

It should be understood that the invention is not limited to the above-described embodiment, but may be modified into various forms on the basis of the spirit of the invention. Additionally, the modifications are included in the scope of the invention. 

What is claimed is:
 1. A linear-compressor moving component support structure, comprising: a moving component partitioning a compressor container of the linear compressor into a high-pressure chamber and a low-pressure chamber for a working gas, the moving component being configured to reciprocate periodically along axially opposite directions in a predetermined range of axial movement, in one of the opposite directions of which the moving component compresses the working gas in the high-pressure chamber; a plurality of axially arranged leaf spring parts, each leaf spring part elastically supporting the moving component in the compressor container such as to allow the axially reciprocating movement of the moving component; a plurality of axially arranged first auxiliary spring parts each having a first axial rigidity, each first auxiliary spring part being located adjacent to one of opposite sides of a corresponding one of the plurality of leaf spring parts; and a plurality of axially arranged second auxiliary spring parts each having a second axial rigidity, each second auxiliary spring part being located adjacent to the other of the opposite sides of a corresponding leaf spring part; wherein the second axial rigidity is different from the first axial rigidity such as to correct deviation, arising due to pressure differences between the high- and low-pressure chambers exerted on the moving component, of actual range of axial movement of the moving component from the predetermined range of axial movement of the moving component.
 2. The moving component support structure according to claim 1, wherein: the predetermined range of axial movement is defined such that a central position of periodic axial elastic deformation of the leaf spring parts in the axially reciprocating movement of the moving component is aligned with a neutral position of the leaf spring parts; and the second axial rigidity is different from the first axial rigidity such as to correct deviation in axial position of the central position from the neutral position of the leaf spring parts.
 3. The moving component support structure according to claim 1, wherein: each first auxiliary spring part is disposed adjacent to the one of the opposite sides of the corresponding leaf spring part in such a way that elastic deformation of the corresponding leaf spring part toward the one of the opposite sides brings the first auxiliary spring part into contact with the corresponding leaf spring part, whereby the first auxiliary spring part follows the elastic deformation of the corresponding leaf spring part toward the one of the opposite sides, and each second auxiliary spring part is disposed adjacent to the other of the opposite sides of the corresponding leaf spring part in such a way that elastic deformation of the corresponding leaf spring part toward the other of the opposite sides brings the second auxiliary spring part into contact with the corresponding leaf spring part, whereby the second auxiliary spring part follows the elastic deformation of the corresponding leaf spring part toward the other of the opposite sides.
 4. The moving component support structure according to claim 1, wherein: each first auxiliary spring part includes one or more first auxiliary springs arranged axially stacked between two axially adjacent leaf spring parts; each second auxiliary spring part includes one or more second auxiliary springs arranged axially stacked between two axially adjacent leaf spring parts; and the number of first auxiliary springs is different from the number of second auxiliary springs.
 5. The moving component support structure according to claim 4, wherein the first auxiliary springs have the same dimension as, and are made of the same material as, the second auxiliary springs.
 6. The moving component support structure according to claim 1, wherein the first auxiliary spring parts have a different dimension from that of the second auxiliary spring parts, and/or the first auxiliary spring parts are made of a material different from that of the second auxiliary spring parts.
 7. The moving component support structure according to claim 1, further comprising: a fixed body slidably supporting the moving component axially, and between itself and the moving component forming the high pressure chamber; an intake valve disposed in the moving component so as to supply the working gas from the low pressure chamber to the high pressure chamber; and an outlet valve disposed in the fixed body so as to discharge the working gas from the high pressure chamber; wherein the second auxiliary spring parts' second axial rigidity is greater than the first auxiliary spring parts' first axial rigidity.
 8. A linear-compressor moving component support structure, comprising: a moving component partitioning a compressor container of the linear compressor into a high-pressure chamber and a low-pressure chamber for a working gas, the moving component being configured to reciprocate periodically along axially opposite directions, in one of the opposite directions of which the moving component compresses the working gas in the high-pressure chamber; a fixed body slidably supporting the moving component axially, and between itself and the moving component forming the high pressure chamber; an intake valve disposed in the moving component so as to supply the working gas from the low pressure chamber to the high pressure chamber; an outlet valve disposed in the fixed body so as to discharge the working gas from the high pressure chamber; a plurality of axially arranged leaf spring parts, each leaf spring part elastically supporting the moving component in the compressor container such as to allow the axially reciprocating movement of the moving component; a plurality of axially arranged first auxiliary spring parts each having a first axial rigidity, each first auxiliary spring part being located adjacent to one of opposite sides of a corresponding one of the plurality of leaf spring parts; and a plurality of axially arranged second auxiliary spring parts each having a second axial rigidity greater than the first axial rigidity, each second auxiliary spring part being located adjacent to the other of the opposite sides of a corresponding leaf spring part.
 9. A linear compressor comprising the moving component support structure according to claim
 1. 10. A cryogenic refrigerator comprising the linear compressor according to claim
 9. 